1. Field of the Invention
This present invention is related to a semiconductor device having integrated metal-oxide-semiconductor field-effect transistor (MOSFET) and Schottky diode and manufacturing method thereof, and more particularly, to a semiconductor device having integrated trench MOS barrier Schottky (TMBS) and manufacturing method thereof.
2. Description of the Prior Art
A Schottky diode is constructed by a metal-to-semiconductor interface where this interface is known to have rectifying characteristics as a PN-junction diode. Moreover, Schottky diode provides rectification as a result of unipolar current transport across the metal-semiconductor contact. Consequently, the Schottky diode has advantage of lower threshold voltage and faster response speed when switching between forward and reverse bias voltage over the PN-junction diode. Thus Schottky diode is widely used in power converter for reducing power consumption and improving switching speed. For instance, a semiconductor device having integrated MOSFET and Schottky diode achieves the goal of reducing power consumption by adopting advantages of Schottky diode such as lower forward voltage (Vf) than that of the body diode of a MOSFET, superior reverse recovery, and faster dynamic response time.
Conventionally, the MOSFET of the conventional power converter is electrically connected in parallel with an external Schottky diode. But it suffers higher production cost and unavoidable parasitic inductances generated when electrically connecting the external Schottky diode to the MOSFET. Therefore, semiconductor device having integrated trench MOSFET and Schottky diode, namely TMBS, is developed. Please refer to FIG. 1, which is a schematic drawing of a conventional TMBS device. As shown in FIG. 1, the conventional TMBS device includes an N-type substrate 100 having an epitaxial silicon layer 102 and a plurality of trenches 104a, 104b formed thereon. The trenches 104a, 104b have the same depth and width. The TMBS device also includes at least a MOSFET 110 and a Schottky diode 120 positioned on the substrate 100. The MOSFET 110 includes a trenched gate 110 formed in the trench 104a, and an N-type heavily doped source 118. The trenched gate 116 is constructed by a thin dielectric layer 112 and a conductive layer 114 filling the trenches 104a. The Schottky diode 120 includes the same dielectric layer 112, the same conductive layer 114 filling the trench 104b, and a metal layer 122, which contacts the substrate 100 between the trenches 104b, serving as an anode of the Schottky diode 120. A surface of the substrate opposite to the surface having the MOSFET 110 and the Schottky diode 120 has a metal layer 106 formed thereon. The metal layer 106 serves as a drain of the MOSFET 110 and a cathode of the Schottky diode 120.
Although TMBS achieves integration of the MOSFET 110 and the Schottky diode 120, it is getting more and more complicated and strict to form the thin dielectric layer 112 and the conductive layer 114 in the trenches 104a, 104b on a demand for higher density, higher efficiency and higher voltage tolerance. Same consideration also emerges when integrating TMBS with other high-density process such as tungsten process. Therefore, a TMBS and manufacturing method thereof that is able to satisfy said demands is still in need.